1. Field of the Invention
The present invention relates to a seismic isolation apparatus, and to an item of equipment such as an automatic vending machine, or a structure like a building, which uses the seismic isolation apparatus.
2. Prior Art
In a seismic isolation apparatus, an ideal seismic isolation is a case in which a friction coefficient is zero. In this case, even in the event that a supporting surface shakes due to an earthquake, its body does not move at all. In the event that the friction coefficient is not zero, but exists even slightly, the body moves, and there is a possibility of a residual displacement occurring after the earthquake. However, in the event that it is possible to easily recover the residual displacement, there is no problem as an anti-earthquake measure. However, the friction coefficient being too low, so that the body moves easily at a time of regular use, is a problem. Designing is done to attain a friction coefficient that satisfies both. Generally, in order to reduce the friction coefficient, as well as using bearings or a material such as tetrafluoroethylene, there is a method whereby a contact surface pressure per unit area is increased. In order to do so, a measure whereby a contact surface is reduced being adopted, as examples adopting this kind of device to date, for example, ones in which there is a contact between planar members or curved members, which have a predetermined area, have been known (refer to JP-A-2000-74138 and JP-A-2002-39266).
Also, in the event of constructing a seismic isolated building using the heretofore described kind of seismic isolation apparatus, an example has been known in which, in order to build at a low cost, structures duplicatively disposed above and below the seismic isolation apparatus are simply constructed (refer to JP-A-2003-293614). In this case, a tabular foundation slab is constructed of ferroconcrete, below a building planar surface, as a foundation structure, and an upper surface thereof is made horizontal. A slip bearing, or the like, to be attached to the foundation slab is driven in to the same height as the upper surface of the concrete. A slip plate, or the like, to be attached to a concrete upper slab, is disposed on the upper surface of the foundation slab, a rubber air jack is disposed in an appropriate place, an arrangement of bars is carried out thereon, and concrete of the upper slab is cast. After the concrete hardens, air is injected into the air jack, the concrete upper slab is lifted up, the slip bearing main body, or the like, is disposed, the air is released from the air jack, and the concrete upper slab is lowered to a predetermined height.
However, with the heretofore described kind of previously known seismic isolation apparatus, not only is an overall height of the seismic isolation apparatus large, meaning that an effective utilization of space cannot be achieved, but also it is not possible to acquire a sufficiently low friction. Meanwhile, in the event of making a contact area small without limit, and forming a mechanical catch in a pointed form, the friction coefficient is raised too far instead. In attempting to avoid such a biting from occurring, surface hardness is also an important factor.
Also, with a building using the heretofore known seismic isolation apparatus, operations of inserting the air jack between the upper and lower slabs, and lifting the upper slab after the concrete hardens, are necessary operations that are troublesome, cause the construction schedule to lengthen, and cause the cost to soar. Furthermore, as the slip bearing main body is inserted under the concrete upper slab, it not being possible to insert it all the way on an interior side, a disposition of the slip bearing main body is restricted to a peripheral edge portion in a range reachable by hand. Thus, a problem to be solved lies in manufacturing, as a simple configuration and at a low cost, a seismic isolation apparatus with a low friction coefficient and a high surface hardness, and furthermore, using it in a seismic isolation structure, such as a small or medium scale building, by a simple method and at a low cost.